1. Field of the Invention
The present invention relates to a batch-type thermal processing apparatus configured to thermally process objects to be processed, such as semiconductor wafers, and a cooling method.
2. Description of Related Art
In general, when semiconductor devices are manufactured, semiconductor wafers of silicon substrates are repeatedly subjected to various processes such as a film-deposition process, an etching process, an oxidation and diffusion process, and an annealing process. When a thermal process such as a film-deposition process is performed by a batch-type thermal processing apparatus capable of simultaneously processing a plurality of semiconductor wafers, it is necessary to cool high-temperature semiconductor wafers as fast as possible, while preventing damages such as slips on the semiconductor wafer, in order to improve a product throughput.
For this purpose, the following thermal processing apparatus is proposed as a conventional batch-type thermal processing apparatus. Namely, in response to the finish of a thermal process of semiconductor wafers, a cooling air is allowed to flow through a space on an outer peripheral side of a vertical processing vessel containing therein the semiconductor wafers. Thus, heat is rapidly drawn from the processing vessel at a high temperature of, e.g., about 800° C. to 1000° C., whereby the high-temperature processed semiconductor wafers can be rapidly cooled (for example, Patent Documents 1 to 5).
The cooling air is sent by a blowing fan to the cooling space around a sidewall of the processing vessel, and is sucked from the cooling space by a suction fan. In this case, although depending on the process manner, the temperature of the cooling air having cooled the processing vessel is raised to reach a temperature as high as about 400° C. to 500° C., and thus the cooling air becomes a high-temperature air. When the high-temperature air directly flows into the suction fan, the suction fan is thermally damaged. Thus, a heat exchanger is disposed on an upstream side of the suction fan, so as to cool the high-temperature air to a predetermined lower temperature such as 50° C., in order that the blowing fan is not thermally damaged.